The benefits of using different tones of gray to create a base for ink-jet printed color images are known. By the same token, in order to create inkjet printed black and white (grayscale) images, several different tones of gray ink are needed. Such gray inks are usually created one of two ways. They can be created by diluting black ink which results in hue shifts upon dilution. On media, gray can also be obtained by mapping other colors (magenta, cyan, yellow) to get the desired hue. Such mapping of other colored inks usually results in a high ink flux on the media which results in loss of detail in dark areas. In 3-ink systems these inks require a high dye load for adequate chroma, which results in high grain due to first-drop visibility. Additionally, prints made with colored inks to map out neutral and gray areas of a print are subject to degradation due to humidity, or a lack of humidfastness, because dyes migrate in media at different rates, and the neutral or gray areas of an image will take on the hue of the dye or dyes that migrate the farthest. In 2-pen 6-ink printing using CMYcmk, images can take on the hue of the inks in the pen with the lighter drop weight.
These defects are predominant in gray and neutral areas of an image. These multi-dye inks cause the greyscale to be unbalanced resulting in color-shifted images.